1. Technical Field
The present invention relates to performance improvements of semiconductor transistors, and more particularly, to the use of halo implants to improve performance of semiconductor transistors.
2. Related Art
In the fabrication process of a typical semiconductor transistor, halo implant is a fabrication step which involves the doping of regions beneath the lightly-doped source/drain (S/D) extension regions of the transistor so as to form halo regions. For each of such halo regions, only the portion under the gate region (called undercutting portion) is useful, and therefore desirable, whereas the rest of the halo region has the effect of reducing the doping concentration of the respective S/D region (called the S/D doping reduction effect), which is undesirable.
Therefore, there is a need for a novel method for forming a halo region that minimizes the S/D doping reduction effect.